The present invention relates to a transport and transfer device.
A device of this type is known from EP-0 591 706. A workpiece in the form of a disc is fixed in a star-shaped transport arrangement by clamping it between a permanent magnet on the device and an armature piece.
In a transfer area to an additional transport device the armature is lifted off its seat, against the force of the permanent magnet, under control of an electromagnet so that the disc-shaped workpiece is released for transfer by means of a mechanically actuated holder on the additional transport device.
Conversely, that is, for transfer in the opposite direction, the armature is released by the electromagnet and placed on the workpiece clamped by a mechanically actuated holder so that it is picked up at the receiving transport device by the force of the permanent magnet. The workpiece is then released to the receiving transport device by the mechanically actuated holder.
The disadvantage of this design is that there is a mechanically actuated and controlled arrangement on the one device. In addition to the complex design the mechanical movements are problematic under vacuum conditions: It promotes particle formation which leads to higher workpiece reject rates. The greater the number of mechanically moved parts in the vacuum atmosphere the greater the potential for faults in the process execution which consequently impairs the reliability of the equipment. In addition this mechanical holder increases the cycle time of the overall system which ultimately increases the manufacturing and operating costs of the system and thereby the costs for the processed workpieces.
The objective of this invention is to eliminate the disadvantages of a device of the aforementioned type.
This is achieved in accordance with the present invention by fitting both arrangements which are movable relative to each other with at least one magnet, each as part of the controllable magnet arrangement, and by having said magnet with the armature part forming a workpiece holder in both arrangements, and by controlling the magnet arrangement in the transfer area in such a way that the armature of one or the other arrangement becomes holding, a device without any mechanical joints, meshing parts, etc. is achieved. This significantly improves the reliability of the device. The transfer cycle time can be significantly reduced, preferably by more than 25%, for example, as in the case of the subsequently described device, from the usual 10 sec. to less than 7.5 sec. This results in significant cost reductions, on the one hand due to the simplicity of the design, in the manufacture of a corresponding system, as well as in the operating costs and consequently the production costs of the workpieces treated by the system.
If workpieces, and in particular disc-shaped workpieces such as mini-disks, compact disks, hard disks, MO disks or semiconductor wafers are to be surface-masked before treatment in the system with a device according to the invention, at least one of the armature parts is simultaneously used as a masking element so that the holder, transfer function and masking can be optimally combined. In this way the aforementioned advantages can be even better realized.
The preferred designs of the device according to the invention, their implementation on a vacuum chamber or a vacuum treatment system as well as the basic transport and transfer techniques according to the invention, and the preferred utilization, are described below.